The present invention relates generally to the field of ophthalmics, more particularly to ophthalmic devices, and still more particularly to ophthalmic devices known as intraocular lenses (IOLs).
Intraocular lenses (IOLs) are commonly used to modify or enhance vision. IOLs can be placed at various positions or locations within the eye. For example, IOLs can be placed in the anterior chamber (AC) of the eye, that is, the region of the eye posterior of the cornea and anterior of the iris. The most common form of such an IOL includes a central lens and outer fixation members or haptics that resiliently contact the annular angle between the cornea and iris.
Although there are substantial advantages to placing the IOL in the anterior chamber of the eye, various complications with angle-supported lenses have been reported. Among other problems, angle-supported anterior chamber IOLs have been reported to cause irritation of the tissue in the angle, and decentration or offsetting displacement away from a preferred optical axis.
Consequently, there has been renewed interest in IOLs constructed for fixation to the iris (some of the earliest IOLs were iris fixated, anterior chamber IOLs), so-called xe2x80x9ciris-supportedxe2x80x9d lenses. By fixing the optic supporting structure to the iris itself, contact with the sensitive filtration angle of the eye is avoided.
Iris fixated IOLs are disclosed in Worst, U.S. Pat. Nos. 4,215,440 and 5,192,319, and in Portney, U.S. Pat. No. 6,152,959. These patents disclose IOLs employing one or more optic fixation members formed having a pair of pincer arms which, acting together, pinch an anterior surface region of the iris. This pinching action detachably attaches the IOL to the iris so that the IOL optic is ideally fixated in the region of the iris opening (i.e., the pupil of the eye). In early designs, the tips of the pincer arms contacted each other, which potentially damaged or even necrosed the iris tissue. In later designs, such as in, Worst, U.S. Pat. No. 5,192,319, the tips of the pincer arms define a gap therebetween which reduces somewhat the tissue damage. However, there is a potential risk that tissue can be damaged by the sharp pincher arms which can puncture the iris tissue.
It would be advantageous to provide iris-supported anterior chamber IOLs which improve on the designs of the prior art.
New IOLs for implantation in eyes, in particular in anterior chambers of the eyes, have been discovered. The present IOLs are sized and structured to reduce the incidence of one or more known complications in the eye caused by prior iris-supported anterior chamber IOLs.
In one embodiment, the present invention provides an iris-supported intraocular lens for implantation in the anterior chamber of an eye, comprising an optic centered on an optical axis and at least two fixation members extending outward from the optic. Each fixation member defines a pair of separated pincer arms that converge toward one another and terminate at aligned end tips to form a gap therebetween. At least one compliant sleeve covers one of the pincer arm tips and fills the gap. There are desirably two sleeves provided for each fixation member, one sleeve covering each pincer arm end tip. Alternatively, there is only one sleeve provided covering one of the pincer arm end tips.
In a preferred embodiment, each fixation member defines a D-shape with a base region forming the upright of the D and the pincer arms forming the curved portion. Alternatively, each fixation member defines an O-shape with a base region adjacent the optic that is narrower than a separation distance between the pair of pincer arms.
The gap desirably has a dimension G of between about 0.004-0.020 inches (0.102-0.508 mm). The pincer arms are typically made of PMMA, and the sleeve is made of a material that has a durometer of less than about 80, desirably less than about 50 at normal eye temperatures (about 35xc2x0 C., just under normal body temperature). For example, the sleeve is made of a material selected from the group consisting of silicone, hydrophobic acrylic, and hydrophylic acrylic. The sleeve desirably has abrupt corners at its distal tip to facilitate grasping of tissue.
In another embodiment, an iris-supported intraocular lens for implantation in the anterior chamber of an eye comprises an optic centered on an optical axis, and at least two fixation members extending outward from the optic. In the alternative embodiment each fixation member defines a pair of separated pincer arms of a first material having a first hardness that converge toward one another and terminate at aligned end tips form a gap therebetween, and an interface of a second material positioned within the gap that is more compliant than the first material of the pincer arms. In a preferred embodiment, the interface comprises a sleeve covering one of the pincer arm end tips and filling the gap, and there are desirably two sleeves provided for each fixation member, one sleeve covering each pincer arm end tip. The at least one of the sleeves desirably has an abrupt edge at its distal tip to facilitate grasping of tissue between the sleeves.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.
These and other aspects and advantages of the present invention will become apparent in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.